1. Related Art
The present invention relates to a method of manufacturing a vacuum chamber which is used as a cluster tool, a vacuum film-forming apparatus, or the like of a manufacturing apparatus used for semiconductors, liquid crystals, solar cells, and the like, and which is used as an apparatus for manufacturing semiconductors, liquid crystals and the like, the pressure within the vacuum chamber being determined by its application and purpose in a range from a low vacuum close to the atmosphere to an ultra-high vacuum. More particularly, the present invention relates to novel improvements for manufacturing a vacuum chamber by forging.
2. Related Art
As the conventional methods of manufacturing a chamber of this type, a method in which a rolled plate-shaped material 10 to machining as it is, as well as a method in which the chamber is fabricated with a welded structure, are known.
With the conventional machining method, as shown in FIG. 6, since a fibrous structure 13 is formed along the rolling direction of the plate material 10, very small spaces exist in the direction of the fibers, and the very small spaces are liable to occur on machined surfaces facing the vacuum. Since the portion indicated at reference numeral 12 at the inner surface of a vacuum chamber 11 is a perpendicularly sectioned portion of the fibrous structure 13, and the very small spaces are deeply entrapped inside the material, the following problems are encountered.
In a case where the chamber is used as a vacuum chamber, the very small spaces result in an increase in the amount of gas released from the interior of the material and in lengthened release time.
Further, if water, contaminants, or the like has entered the very small spaces, they are difficult to be removed even under a vacuum condition, and the time until a required degree of vacuum is reached by the continuous discharging of air by a vacuum pump is appreciably delayed.
For this reason, the time until the processing of wafers or the like inside the chamber becomes possible is delayed (leads to a reduction in throughput). This constitutes a cause which deteriorates the performance of the vacuum chamber.
In addition, with the method in which the vacuum chamber is fabricated with a welded structure, very small cracks are liable to occur in the welds, and there occurs the phenomenon in which the gas fused in the beads during welding is emitted under vacuum for a long time, and adverse effects are often exerted on the performance of the vacuum chamber in the same way as described above. With the conventional machining method in which the rolled plate-shaped material is subjected to machining as it is, since a fibrous structure 13 is formed along the rolling direction of the plate material as shown in FIG. 6, very small spaces are exposed to the inner surfaces of the vacuum chamber as perpendicularly sectioned portions of the fibers, and the very small spaces are liable to be produced on the machined surfaces.
In an application to the vacuum chamber, as described above, these very small spaces cause an increase in the amount of gas released from the interior of the material, and water, contaminants and the like which entered the vary small spaces are difficult to be removed under a high vacuum, thereby exerting adverse effects to the performance of the vessel.
In addition, in recent years the apparatus tends to become larger in size.
For example, the diameters of silicon wafers processed by a semiconductor manufacturing apparatus are shifting from 8 inches (about 200 mm) to 12 inches (about 300 mm), and the manufacturing apparatus is becoming large correspondingly. For this reason, in cases where the chamber is fabricated by cutting out a plate material, the amount of material to be removed from the interior of the chamber is large, so that the manufacturing cost is tending to become high.
Furthermore, with the method in which the vacuum chamber is fabricated with the welded structure, very small cracks are liable to occur since the welds are even longer in conjunction with the need for the large-sized chamber, and adverse effects are often exerted on the performance of the vacuum chamber.